implementing op codes

.idea/dictionaries/project.xml

@@ -5,6 +5,12 @@
       <w>adcn</w>
       <w>addhl</w>
       <w>addsp</w>
+      <w>dechl</w>
+      <w>inchl</w>
+      <w>jpcc</w>
+      <w>jphl</w>
+      <w>jrcc</w>
+      <w>reti</w>
       <w>rrca</w>
       <w>rrla</w>
     </words>

src/instructions.rs

@@ -1,5 +1,5 @@
+use crate::registers::FlagsRegister;
 use crate::registers::Registers;
-
 struct CPU { 
     registers: Registers,
     pc: u16,
@@ -19,12 +19,46 @@ impl MemoryBus {
     }
 
 }
-
+#[derive(Clone, Copy)]
 enum Target {
     U8Register(TargetRegister),
     U16Register(TargetU16Register),
     Address(u16),
 }
+#[derive(Clone, Copy)]
+enum Condition {
+    NZ, // Not Zero
+    Z,  // Zero
+    NC, // Not Carry
+    C,  // Carry
+    None
+}
+
+#[derive(Clone, Copy)]
+enum LoadTarget{
+    CopyR8R8(TargetRegister, TargetRegister),
+    CopyR8N8(TargetRegister, u8),
+    CopyR16N16(TargetU16Register, u16),
+    CopyHLR8(TargetRegister),
+    CopyHLN8(u8),
+    CopyR8HL(TargetRegister),
+    CopyR16A(TargetU16Register),
+    CopyN16A(u16),
+    CopyHN16A(u16),
+    CopyHCA,
+    CopyAR16(TargetU16Register),
+    CopyAN16(u16),
+    CopyHAN16(u16),
+    CopyHAC,
+    CopyHLIA,
+    CopyHLDA,
+    CopyAHLD,
+    CopyAHLI,
+    CopySPN16(u16),
+    CopyN16SP(u16),
+    CopyHLSPE8(i8),
+    CopySPHL,
+}
 
 
 enum Instruction {
@@ -34,27 +68,60 @@ enum Instruction {
     ADDSP(u8),
     AND(Target),
     BIT(u8, Target),
-    CALL(u16),
+    CALL(Condition, u16),
-    
-    SUB(TargetRegister),
-    SBC(TargetRegister),
-    
-    OR(TargetRegister),
-    XOR(TargetRegister),
-    CP(TargetRegister),
-    INC(TargetRegister),
-    DEC(TargetRegister),
     CCF,
-    SCF,
+    CP(Target),
-    RRA,
-    RLA,
-    RRCA,
     CPL,
-    
+    DAA,
+    DEC(Target),
+    DECHL(TargetU16Register),
+    DI,
+    EI,
+    HALT,
+    INC(Target),
+    INCHL(TargetU16Register),
+    JP(Condition, u16),
+    JPHL,
+    JR(Condition, i8),
+    LD(LoadTarget),
+    NOP,
+    OR(Target),
+    POP(TargetU16Register),
+    PUSH(TargetU16Register),
+    RES(u8, Target),
+    RET(Condition),
+    RETI,
+    RL(Target),
+    RLC(Target),
+    RR(Target),
+    RRC(Target),
+    RST(u8),
+    SBC(Target),
+    SCF,
+    SET(u8, Target),
+    SLA(Target),
+    SRA(Target),
+    SRL(Target),
+    STOP,
+    SUB(Target),
+    SWAP(Target),
+    XOR(Target),
 }
+#[derive(Clone, Copy)]
 enum TargetRegister { A, B, C, D, E, H, L, }
+#[derive(Clone, Copy)]
 enum TargetU16Register {AF, BC, DE, HL, SP, PC}
 impl CPU {
+    fn check_condition(&self, condition: Condition) -> bool {
+        match condition {
+            Condition::NZ => !self.registers.f.zero,
+            Condition::Z => self.registers.f.zero,
+            Condition::NC => !self.registers.f.carry,
+            Condition::C => self.registers.f.carry,
+            Condition::None => true,
+        }
+    }
+
     fn get_u8_reg_value(&mut self, target: TargetRegister) -> u8 {
         match target {
             TargetRegister::A => { self.registers.a }
@@ -66,6 +133,17 @@ impl CPU {
             TargetRegister::L => { self.registers.l }
         }
     }
+    fn set_u8_reg_value(&mut self, target: TargetRegister, value: u8) {
+        match target {
+            TargetRegister::A => { self.registers.a = value }
+            TargetRegister::B => { self.registers.b = value }
+            TargetRegister::C => { self.registers.c = value }
+            TargetRegister::D => { self.registers.d = value }
+            TargetRegister::E => { self.registers.e = value }
+            TargetRegister::H => { self.registers.h = value }
+            TargetRegister::L => { self.registers.l = value }
+        }
+    }
     fn get_u16_reg_value(&mut self, target: TargetU16Register) -> u16 {
         match target {
             TargetU16Register::AF => {self.registers.get_af()}
@@ -76,6 +154,29 @@ impl CPU {
             TargetU16Register::PC => {self.pc}
         }
     }
+    fn set_u16_reg_value(&mut self, target: TargetU16Register, value: u16) {
+        match target {
+            TargetU16Register::AF => {self.registers.set_af(value)}
+            TargetU16Register::BC => {self.registers.set_bc(value)}
+            TargetU16Register::DE => {self.registers.set_de(value)}
+            TargetU16Register::HL => {self.registers.set_hl(value)}
+            TargetU16Register::SP => {self.sp=value}
+            TargetU16Register::PC => {self.pc=value}
+        }
+    }
+    fn push_stack(&mut self, value: u16) {
+        let low = (value & 0xFF) as u8;
+        let high = (value >> 8) as u8;
+        self.bus.write_byte(self.sp - 1, high);
+        self.bus.write_byte(self.sp - 2, low);
+        self.sp = self.sp.wrapping_sub(2);
+    }
+    fn pop_stack(&mut self) -> u16 {
+        let low = (self.bus.read_byte(self.sp) as u16) << 8;
+        let high = self.bus.read_byte(self.sp + 1) as u16;
+        self.sp = self.sp.wrapping_add(2);
+        high | low
+    }
     
     fn get_target_value(&mut self, target: Target) -> u8 {
         match target {
@@ -87,6 +188,16 @@ impl CPU {
             Target::Address(address) => { self.bus.read_byte(address) },
         }
     }
+    fn set_target_value(&mut self, target: Target, value: u8) {
+        match target {
+            Target::U8Register(target_register) => { self.set_u8_reg_value(target_register, value) },
+            Target::U16Register(target_register) => {
+                let address = self.get_u16_reg_value(target_register);
+                self.bus.write_byte(address, value)
+            },
+            Target::Address(address) => { self.bus.write_byte(address, value) },
+        }
+    }
 
     ///
     fn execute(&mut self, instruction: Instruction) {
@@ -142,33 +253,311 @@ impl CPU {
                 self.registers.f.subtract = false;
                 self.registers.f.half_carry = true;
             }
-            Instruction::CALL(address) => {
+            Instruction::CALL(condition, address) => {
-                // Decrement stack pointer
+                if self.check_condition(condition) {
                     self.sp = self.sp.wrapping_sub(2);
-                
                     let pc = self.pc;
                     self.bus.write_byte(self.sp + 1, ((pc >> 8) & 0xFF) as u8);
                     self.bus.write_byte(self.sp, (pc & 0xFF) as u8);
-
-                // Jump to the target address
                     self.pc = address;
                 }
-
+            }
-
+            Instruction::CCF => {
-
+                self.registers.f.subtract = false;
-
+                self.registers.f.half_carry = false;
-
+                self.registers.f.carry = !self.registers.f.carry;
-            Instruction::SUB(target) => {
+            }
-                let value = self.get_u8_reg_value(target);
+            Instruction::CP(target) => {
+                let value = self.get_target_value(target);
                 let (new_value, did_overflow) = self.registers.a.overflowing_sub(value);
-                self.registers.a = new_value;
                 self.registers.f.zero = new_value == 0;
                 self.registers.f.subtract = true;
                 self.registers.f.carry = did_overflow;
                 self.registers.f.half_carry = (self.registers.a & 0xF) + (value & 0xF) > 0xF;
             }
-            Instruction::SBC(target) => {
+            Instruction::CPL => {
+                self.registers.a = !self.registers.a;
+                self.registers.f.subtract = true;
+                self.registers.f.half_carry = true;
+            }
+            Instruction::DAA => {
+                let new_value;
+                let did_overflow;
+                let mut adjustment: u8 = 0;
+                if self.registers.f.subtract {
+                    if self.registers.f.half_carry {
+                        adjustment += 0x6;
+                    }
+                    if self.registers.f.carry {
+                        adjustment += 0x60;
+                    }
+                    (new_value, did_overflow) = self.registers.a.overflowing_sub(adjustment);
+                } else {
+                    if self.registers.f.half_carry || self.registers.a & 0xF > 0x9 {
+                        adjustment += 0x6;
+                    }
+                    if self.registers.f.carry || self.registers.a > 0x99 {
+                        adjustment += 0x60;
+                    }
+                    (new_value, did_overflow) = self.registers.a.overflowing_add(adjustment);
+                }
+                self.registers.a = new_value;
+                self.registers.f.carry = did_overflow;
+                self.registers.f.zero = new_value == 0;
+                self.registers.f.half_carry = false;
+            }
+            Instruction::DEC(target) => {
+                match target {
+                    Target::U8Register(target) => {
                         let value = self.get_u8_reg_value(target);
+                        let (new_value, _) = value.overflowing_sub(1);
+                        self.set_u8_reg_value(target, new_value);
+                        self.registers.f.zero = new_value == 0;
+                        self.registers.f.subtract = true;
+                        self.registers.f.half_carry = (new_value & 0xF) + (value & 0xF) > 0xF;
+                    }
+                    Target::U16Register(target) => {
+                        let value = self.get_u16_reg_value(target);
+                        let new_value = value.wrapping_sub(1);
+                        self.set_u16_reg_value(target, new_value);
+                    }
+                    Target::Address(_) => {}
+                }
+            }
+            Instruction::DECHL(register) => {
+                let target = Target::U16Register(register);
+                let value = self.get_target_value(target);
+                let new_value = value.wrapping_sub(1);
+                self.set_target_value(target, new_value);
+                self.registers.f.zero = new_value == 0;
+                self.registers.f.subtract = true;
+                self.registers.f.half_carry = (new_value & 0xF) + (value & 0xF) > 0xF;
+            }
+            Instruction::DI => {}
+            Instruction::EI => {}
+            Instruction::HALT => {todo!();}
+
+            Instruction::INC(target) => {
+                match target {
+                    Target::U8Register(target) => {
+                        let value = self.get_u8_reg_value(target);
+                        let (new_value, _) = value.overflowing_add(1);
+                        self.set_u8_reg_value(target, new_value);
+                        self.registers.f.zero = new_value == 0;
+                        self.registers.f.subtract = false;
+                        self.registers.f.half_carry = (new_value & 0xF) + (value & 0xF) > 0xF;
+                    }
+                    Target::U16Register(target) => {
+                        let value = self.get_u16_reg_value(target);
+                        let new_value = value.wrapping_add(1);
+                        self.set_u16_reg_value(target, new_value);
+                    }
+                    Target::Address(_) => {}
+                }
+            }
+            Instruction::INCHL(register) => {
+                let target = Target::U16Register(register);
+                let value = self.get_target_value(target);
+                let new_value = value.wrapping_add(1);
+                self.set_target_value(target, new_value);
+                self.registers.f.zero = new_value == 0;
+                self.registers.f.subtract = true;
+                self.registers.f.half_carry = (new_value & 0xF) + (value & 0xF) > 0xF;
+            }
+            Instruction::JP(condition, address) => {
+                if self.check_condition(condition) {
+                    self.pc = address;
+                }
+            }
+            Instruction::JPHL => {
+                self.pc = self.registers.get_hl();
+            }
+            Instruction::JR(condition, offset) => {
+                if self.check_condition(condition) {
+                    self.pc = if offset.is_negative() {
+                        self.pc.wrapping_sub(offset.abs() as u16)
+                    } else {
+                        self.pc.wrapping_add(offset as u16)
+                    }
+                }
+            }
+            Instruction::LD(target) => {
+                match target {
+                    LoadTarget::CopyR8R8(dest_register, source_register) => {
+                        let value = self.get_u8_reg_value(source_register);
+                        self.set_u8_reg_value(dest_register, value);
+                    }
+                    LoadTarget::CopyR8N8(dest_register, value) => {
+                        self.set_u8_reg_value(dest_register, value);
+                    }
+                    LoadTarget::CopyR16N16(dest_register, value) => {
+                        self.set_u16_reg_value(dest_register, value);
+                    }
+                    LoadTarget::CopyHLR8(source_register) => {
+                        let value = self.get_u8_reg_value(source_register);
+                        let address = self.registers.get_hl();
+                        self.bus.write_byte(address, value);
+                    }
+                    LoadTarget::CopyHLN8(value) => {
+                        let address = self.registers.get_hl();
+                        self.bus.write_byte(address, value);
+                    }
+                    LoadTarget::CopyR8HL(dest_register) => {
+                        let address = self.registers.get_hl();
+                        let value = self.bus.read_byte(address);
+                        self.set_u8_reg_value(dest_register, value);
+                    }
+                    LoadTarget::CopyR16A(dest_register) => {
+                        let address = self.get_u16_reg_value(dest_register);
+                        self.bus.write_byte(address, self.registers.a);
+                    }
+                    LoadTarget::CopyN16A(address) => {
+                        self.bus.write_byte(address, self.registers.a);
+                    }
+                    LoadTarget::CopyHN16A(address) => {
+                        if address >= 0xFF00 {
+                            self.bus.write_byte(address, self.registers.a)
+                        }
+                    }
+                    LoadTarget::CopyHCA => {
+                        let address = 0xFF00 + self.registers.c as u16;
+                        self.bus.write_byte(address, self.registers.a)
+                    }
+                    LoadTarget::CopyAR16(source_register) => {
+                        let address = self.get_u16_reg_value(source_register);
+                        self.registers.a = self.bus.read_byte(address);
+                    }
+                    LoadTarget::CopyAN16(address) => {
+                        self.registers.a = self.bus.read_byte(address);
+                    }
+                    LoadTarget::CopyHAN16(address) => {
+                        if address >= 0xFF00 {
+                            self.registers.a = self.bus.read_byte(address)
+                        }
+                    }
+                    LoadTarget::CopyHAC => {
+                        self.registers.a = self.bus.read_byte(0xFF00+self.registers.c as u16)
+                    }
+                    LoadTarget::CopyHLIA => {
+                        let address = self.registers.get_hl();
+                        self.bus.write_byte(address, self.registers.a);
+                        self.registers.set_hl(address.wrapping_add(1));
+                    }
+                    LoadTarget::CopyHLDA => {
+                        let address = self.registers.get_hl();
+                        self.bus.write_byte(address, self.registers.a);
+                        self.registers.set_hl(address.wrapping_sub(1));
+                    }
+                    LoadTarget::CopyAHLI => {
+                        let address = self.registers.get_hl();
+                        self.registers.a = self.bus.read_byte(address);
+                        self.registers.set_hl(address.wrapping_add(1));
+                    }
+                    LoadTarget::CopyAHLD => {
+                        let address = self.registers.get_hl();
+                        self.registers.a = self.bus.read_byte(address);
+                        self.registers.set_hl(address.wrapping_sub(1));
+                    }
+                    LoadTarget::CopySPN16(value) => {
+                        self.sp = value;
+                    }
+                    LoadTarget::CopyN16SP(address) => {
+                        self.bus.write_byte(address, (0xF & self.sp) as u8);
+                        self.bus.write_byte(address + 1, (self.sp >> 8) as u8);
+                    }
+                    LoadTarget::CopyHLSPE8(value) => {
+
+                        let new_value = match value.is_negative() {
+                            true => { self.sp.wrapping_sub(value.abs() as u16) }
+                            false => { self.sp.wrapping_add(value as u16) }
+                        };
+                        self.registers.set_hl(new_value);
+                        self.registers.f.zero = false;
+                        self.registers.f.subtract = false;
+                        self.registers.f.carry = (new_value & 0xFF) + (self.sp & 0xFF) > 0xFF;
+                        self.registers.f.half_carry = (new_value & 0xF) + (self.sp & 0xF) > 0xF;
+                        
+                    }
+                    LoadTarget::CopySPHL => {
+                        self.sp = self.registers.get_hl();
+                    }
+                }
+            }
+            Instruction::NOP => {}
+            Instruction::OR(target) => {
+                let value = self.get_target_value(target);
+                self.registers.a = value | self.registers.a;
+                self.registers.f.zero = self.registers.a == 0;
+                self.registers.f.subtract = false;
+                self.registers.f.carry = false;
+                self.registers.f.half_carry = false;
+            }
+            Instruction::POP(target) => {
+                let value = self.pop_stack();
+                self.set_u16_reg_value(target, value);
+            }
+            Instruction::PUSH(target) => {
+                let value = self.get_u16_reg_value(target);
+                self.push_stack(value);
+            }
+            Instruction::RES(bit, target) => {
+                let mut value = self.get_target_value(target);
+                value &= !(1 << bit);
+                self.set_target_value(target, value);
+            }
+            Instruction::RET(condition) => {
+                if self.check_condition(condition) {
+                    self.pc = self.pop_stack();
+                }
+            }
+            Instruction::RETI => {
+                self.pc = self.pop_stack();
+            }
+            Instruction::RL(target) => {
+                let old_value = self.get_target_value(target);
+                let old_carry = self.registers.f.carry;
+                self.registers.f.carry = old_value & 0x80 == 0x80;
+                let new_value = (self.registers.a << 1) | (if old_carry { 0x01 } else { 0 });
+                self.set_target_value(target, new_value);
+                self.registers.f.zero = false;
+                self.registers.f.subtract = false;
+                self.registers.f.half_carry = false;
+            }
+            Instruction::RLC(target) => {
+                let old_value = self.get_target_value(target);
+                self.registers.f.carry = old_value & 0x80 == 0x80;
+                let new_value = (self.registers.a << 1) | (if self.registers.f.carry { 0x1 } else { 0 });
+                self.set_target_value(target, new_value);
+                self.registers.f.zero = false;
+                self.registers.f.subtract = false;
+                self.registers.f.half_carry = false;
+            }
+            Instruction::RR(target) => {
+                let old_value = self.get_target_value(target);
+                let old_carry = self.registers.f.carry;
+                self.registers.f.carry = old_value & 0x1 == 0x1;
+                let new_value = (self.registers.a >> 1) | (if old_carry { 0x80 } else { 0 });
+                self.set_target_value(target, new_value);
+                self.registers.f.zero = false;
+                self.registers.f.subtract = false;
+                self.registers.f.half_carry = false;
+            }
+            Instruction::RRC(target) => {
+                let old_value = self.get_target_value(target);
+                self.registers.f.carry = old_value & 0x1 == 0x1;
+                let new_value = (self.registers.a >> 1) | (if self.registers.f.carry { 0x80 } else { 0 });
+                self.set_target_value(target, new_value);
+                self.registers.f.zero = false;
+                self.registers.f.subtract = false;
+                self.registers.f.half_carry = false;
+            }
+            Instruction::RST(idx) => {
+                self.push_stack(self.pc);
+                let address = self.bus.read_byte((idx as u16) * 8) as u16;
+                self.pc = address;
+            }
+            Instruction::SBC(target) => {
+                let value = self.get_target_value(target);
                 let (mut new_value, did_overflow) = self.registers.a.overflowing_sub(value);
                 new_value -= did_overflow as u8;
                 self.registers.a = new_value;
@@ -177,165 +566,72 @@ impl CPU {
                 self.registers.f.carry = did_overflow;
                 self.registers.f.half_carry = (self.registers.a & 0xF) + (value & 0xF) > 0xF;
             }
+            Instruction::SCF => {
+                self.registers.f.carry = true;
+                self.registers.f.subtract = false;
+                self.registers.f.half_carry = false;
+            }
+            Instruction::SET(bit, target) => {
+                let mut value = self.get_target_value(target);
+                value |= 1 << bit;
+                self.set_target_value(target, value);
+            }
+            Instruction::SLA(target) => {
+                let value = self.get_target_value(target);
+                let new_value = value << 1;
+                self.set_target_value(target, new_value);
+                self.registers.f.zero = new_value == 0;
+                self.registers.f.subtract = false;
+                self.registers.f.carry = value & 0x80 == 0x80;
+                self.registers.f.half_carry = false;
+            }
+            Instruction::SRA(target) => {
+                let value = self.get_target_value(target);
+                let new_value = value >> 1 | (if value & 0x80 == 0x80 { 0x80 } else { 0 });
+                self.set_target_value(target, new_value);
+                self.registers.f.zero = new_value == 0;
+                self.registers.f.subtract = false;
+                self.registers.f.carry = value & 0x80 == 0x80;
+                self.registers.f.half_carry = false;
+            }
+            Instruction::SRL(target) => {
+                let value = self.get_target_value(target);
+                let new_value = value >> 1;
+                self.set_target_value(target, new_value);
+                self.registers.f.zero = new_value == 0;
+                self.registers.f.subtract = false;
+                self.registers.f.carry = value & 0x1 == 0x1;
+                self.registers.f.half_carry = false;
+            }
+            Instruction::STOP => {
                 
-            Instruction::OR(target) => {
+            }
-                let value = self.get_u8_reg_value(target);
+            Instruction::SUB(target) => {
-                self.registers.a = value | self.registers.a;
+                let value = self.get_target_value(target);
-                self.registers.f.zero = self.registers.a == 0;
+                let (new_value, did_overflow) = self.registers.a.overflowing_sub(value);
+                self.registers.a = new_value;
+                self.registers.f.zero = new_value == 0;
+                self.registers.f.subtract = true;
+                self.registers.f.carry = did_overflow;
+                self.registers.f.half_carry = (self.registers.a & 0xF) + (value & 0xF) > 0xF;
+            }
+            Instruction::SWAP(target) => {
+                let value = self.get_target_value(target);
+                let new_value = ((value & 0xF0) >> 4) | ((value & 0x0F) << 4);
+                self.set_target_value(target, new_value);
+                self.registers.f.zero = new_value == 0;
                 self.registers.f.subtract = false;
                 self.registers.f.carry = false;
                 self.registers.f.half_carry = false;
             }    
             Instruction::XOR(target) => {
-                let value = self.get_u8_reg_value(target);
+                let value = self.get_target_value(target);
                 self.registers.a = value ^ self.registers.a;
                 self.registers.f.zero = self.registers.a == 0;
                 self.registers.f.subtract = false;
                 self.registers.f.carry = false;
                 self.registers.f.half_carry = false;
             }
-            Instruction::CP(target) => {
-                let value = self.get_u8_reg_value(target);
-                let (new_value, did_overflow) = self.registers.a.overflowing_sub(value);
-                self.registers.f.zero = new_value == 0;
-                self.registers.f.subtract = true;
-                self.registers.f.carry = did_overflow;
-                self.registers.f.half_carry = (self.registers.a & 0xF) + (value & 0xF) > 0xF;
-            }
-            Instruction::INC(target) => {
-                let (value, new_value) = match target {
-                    TargetRegister::A => {
-                        let value = self.registers.a;
-                        let (new_value, _) = value.overflowing_add(1);
-                        self.registers.a = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::B => {
-                        let value = self.registers.b;
-                        let (new_value, _) = value.overflowing_add(1);
-                        self.registers.b = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::C => {
-                        let value = self.registers.c;
-                        let (new_value, _) = value.overflowing_add(1);
-                        self.registers.c = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::D => {
-                        let value = self.registers.d;
-                        let (new_value, _) = value.overflowing_add(1);
-                        self.registers.d = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::E => {
-                        let value = self.registers.e;
-                        let (new_value, _) = value.overflowing_add(1);
-                        self.registers.e = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::H => {
-                        let value = self.registers.h;
-                        let (new_value, _) = value.overflowing_add(1);
-                        self.registers.h = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::L => {
-                        let value = self.registers.l;
-                        let (new_value, _) = value.overflowing_add(1);
-                        self.registers.l = new_value;
-                        (value, new_value)
-                    }
-                };
-                self.registers.f.zero = new_value == 0;
-                self.registers.f.subtract = false;
-                self.registers.f.half_carry = (new_value & 0xF) + (value & 0xF) > 0xF;
-            }
-            Instruction::DEC(target) => {
-                let (value, new_value) = match target {
-                    TargetRegister::A => {
-                        let value = self.registers.a;
-                        let (new_value, _) = value.overflowing_sub(1);
-                        self.registers.a = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::B => {
-                        let value = self.registers.b;
-                        let (new_value, _) = value.overflowing_sub(1);
-                        self.registers.b = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::C => {
-                        let value = self.registers.c;
-                        let (new_value, _) = value.overflowing_sub(1);
-                        self.registers.c = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::D => {
-                        let value = self.registers.d;
-                        let (new_value, _) = value.overflowing_sub(1);
-                        self.registers.d = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::E => {
-                        let value = self.registers.e;
-                        let (new_value, _) = value.overflowing_sub(1);
-                        self.registers.e = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::H => {
-                        let value = self.registers.h;
-                        let (new_value, _) = value.overflowing_sub(1);
-                        self.registers.h = new_value;
-                        (value, new_value)
-                    },
-                    TargetRegister::L => {
-                        let value = self.registers.l;
-                        let (new_value, _) = value.overflowing_sub(1);
-                        self.registers.l = new_value;
-                        (value, new_value)
-                    }
-                };
-                self.registers.f.zero = new_value == 0;
-                self.registers.f.subtract = true;
-                self.registers.f.half_carry = (new_value & 0xF) + (value & 0xF) > 0xF;
-            }
-            Instruction::CCF => {
-                self.registers.f.carry = !self.registers.f.carry;
-            }
-            Instruction::SCF => {
-                self.registers.f.carry = true;
-            }
-            Instruction::RRA => {
-                let old_carry = self.registers.f.carry;
-                self.registers.f.carry = self.registers.a & 0x1 == 0x1;
-                self.registers.a = (self.registers.a >> 1) | (if old_carry { 0x80 } else { 0 });
-                self.registers.f.zero = false;
-                self.registers.f.subtract = false;
-                self.registers.f.half_carry = false;
-            }
-            Instruction::RLA => {
-                let old_carry = self.registers.f.carry;
-                self.registers.f.carry = self.registers.a & 0x80 == 0x80;
-                self.registers.a = (self.registers.a << 1) | (if old_carry { 0x01 } else { 0 });
-                self.registers.f.zero = false;
-                self.registers.f.subtract = false;
-                self.registers.f.half_carry = false;
-            }
-            Instruction::RRCA => {
-                self.registers.f.carry = self.registers.a & 0x1 == 0x1;
-                self.registers.a = self.registers.a >> 1;
-                self.registers.f.zero = false;
-                self.registers.f.subtract = false;
-                self.registers.f.half_carry = false;
-            }
-            Instruction::CPL => {
-                self.registers.a = !self.registers.a;
-                self.registers.f.subtract = true;
-                self.registers.f.half_carry = true;
-            }
-
-            
         }
     }
 }